In recent years, from a perspective of preserving the environment, it is becoming popular to use a power generating apparatus of renewable energy type such as a wind turbine generator utilizing wind power and renewable energy type turbine generator such as a tidal current generator utilizing tidal. In the power generating apparatus of renewable energy type, a motion energy of the wind, the tidal current, the ocean current or the river current rotates the blade and the rotation energy is inputted to the generator via the hub and the main shaft to generate power into electric power by the generator.
For instance, the wind turbine generator is provided with a tower, a nacelle installed atop the tower, a main shaft rotatably attached to the nacelle, a hub connected to the main shaft, blades attached radially to the hub. In this wind turbine generator, the rotation energy of the blade rotated by the wind power is inputted to the generator via the hub and the main shaft to generate electrical power. Further, the wind turbine generator is further provided with a pitch angle control mechanism for controlling the pitch angle of the blade to efficiently extract the wind power energy. The pitch angle control mechanism is also used to reduce the torque of the rotor by changing the pitch angle of the blade toward a feathering position to feather the wind when the load acting on the wind turbine generator increases rapidly.
In such wind turbine generator, when attaching the blade, first the blade is lifted to a height of the nacelle and then a blade root part of the blade and a blade attaching part of the hub are fastened together, thereby attaching the blade to the hub. In such a case that there is enough flat land around the location of the wind turbine generator, the blade may be attached to the hub before mounting the hub to the nacelle.
As related technique, disclosed in Patent Literature 1 is a blade attaching method in which the blade is maintained horizontally when the blade is lifted to the hub. According to the method, an orientation of the blade is maintained substantially the same by use of control wires connecting the blade to a winch. Further, disclosed in Patent Literature 2 is another blade attaching method in which the blade is clamped horizontally by a clamping device and lifted to the hub and then the blade is attached to the hub. Further, disclosed in Patent Literature 3 is yet another blade attaching method in which, when the blade is attached to the hub, the pitch angle of the blade is adjusted. According to this method, the blade is held by a holding device including a frame and a seat. The orientation of the blade is adjusted by rotating the holding device in a direction of the pitch angle.